We investigated sodium-proton (Na + -H + ) exchange activity in transgenic TGR(mRen-2)27 rats, a strain showing fulminant hypertension after the mouse Ren-2 1 renin gene has been integrated into its genome, in age-matched normotensive Sprague-Dawley (SD) rats, in spontaneously hypertensive rats (SHR) from the Munster strain, and in normotensive WistarKyoto (WKY) rats. From each strain Na + -H + exchange activity was determined in lymphocytes using the pH-sensitive fluorescent dye 2',7'-bis(2-carbc«yethyl)-5(6)-carboxyfluorescein acetaxymethyl ester (BCECF-AM) by measuring the recovery rate of cytosolic pH (pH,) after intracellular acidification. Resting pH, was not significantly different in transgenic rats (n=10) compared with SD rats (n=10) (7.305±0.038 versus 7.337±0.031; mean±SEM), but resting pHj was significantly lower in rympho-
Cytosolic pH (pHi) and Na+/H+ exchange activity were measured in lymphocytes from 22 patients with mild chronic renal failure, and 21 age- and sex-matched normotensive healthy control subjects using the fluorescent dye technique. The basal pHi in resting lymphocytes was not significantly different in both groups tested (control, pHi 7.18 ± 0.04; patients with mild chronic renal failure, 7.17 ± 0.05). The initial rate of pHi recovery immediately after intra-cellular acidification with 100 mmol/l propionic acid, representing the maximum Na+/H+ exchange activity, was significantly higher in lymphocytes from patients with mild chronic renal failure (7.10 ± 0.52 dpHi/s, mean ± SEM) when compared with control subjects (5.42 ± 0.47 dpHi/s; p < 0.05). No significant correlation between Na+/H+ exchange activity and blood pressure could be obtained in patients with mild chronic renal failure. Furthermore, there was no relationship of Na+/H+ exchange activity to cytosolic pH or extracellular pH. It is concluded that an enhanced Na+/H+ exchange activity can be detected in patients with mild chronic renal failure and may not be related to the significant abnormalities of electrolyte and acid-base metabolism commonly observed in patients with end-stage renal failure or on hemodialysis.
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